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Full text of "Fall compared to spring application of nitrogen fertilizers in Alberta."

Agriculture 
Canada 



■ * y Agriculture 



Canada 



MAR 3 !993 



Library / Bibliotheque, Ottawa K1A 0C5 







m 



^ 



Research Branch 
Technical Bulletin 1 992-8E 

Fall compared 

to spring 

application of 

nitrogen 

fertilizers in 

Alberta 



Canada 



Cover illustration 

The images represent the Research Branch's objective: 

to improve the long-term competitiveness of the Canadian 

agri-food sector through the development and transfer of new. 

technologies. 

Designed by Research Program Service. 

Illustration de la couverture 

Les dessins illustrent l'objectif de la Direction generate de la 

recherche : ameliorer la competitivite a long terme du secteur 

agro-alimentaire canadien grace aia mise au point et au transfer! 

de nouvelles technologies. 

Conception par le Service aux programmes de recherches. 







Fall compared to 
spring application of 
nitrogen fertilizers in 

Alberta 



S.SMALHI 

Agriculture Canada 

Research Station 

Lacombe, Alberta 

M. NYBORG 

Department of Soil Science 

University of Alberta 

Edmonton, Alberta 

E.D. SOLBERG, DJ. HEANEY 

Soils Branch 

Alberta Agriculture 

Edmonton, Alberta 

Technical Bulletin 1992-8E 



Research Branch 

Agriculture Canada 

1992 



Copies of this publication are available from 

Director 

Research Station 

Research Branch, Agriculture Canada 

Bag Service 5000 

58th SL at the C & E Trail 

Lacombe, Alberta 

T0C1S0 

© Minister of Supply and Services Canada 1992 
Cat. No. A54-8/1992-8E 
ISBN 0-662-20082-9 

Egalement disponible en francais sous le titre 
Comparaison des applications automnales et 
printaniires d'engrais azotis en Alberta 



CONTENTS 

ACKNOWLEDGEMENTS iv 

SUMMARY / RESUME v 

INTRODUCTION 1 

REASONS FOR INFERIORITY OF FALL- APPLIED N 1 

FACTORS AFFECTING EFFICIENCY OF FALL- AND SPRING- APPLIED N 3 

Kind of N Fertilizer 3 

Date of Fall Application 4 

Inhibitors and Slow-Release N Fertilizers 7 

Methods of N Placement 7 

Depth of Placement of Spring-Applied N 11 

Rate of N, Soil Test N0 3 -N and Yield Response 11 

Texture, Drainage and Fall Soil Moisture 12 

Soil-Climatic Zone. 12 

CONCLUSIONS. 13 

RECOMMENDATIONS. 15 

REFERENCES 16 



in 



ACKNOWLEDGMENTS 

The authors thank the Agricultural Research Council of Alberta (Farming for the 
Future Program), Alberta Agriculture Research Trust, Western Co-operative Fertilizers 
Limited and the Sulphur Institute for financial support. Acknowledgment is given to 
Alberta Agriculture Soils and Animal Nutrition Laboratory for certain analyses. 



IV 



SUMMARY 

In Alberta and other Prairie Provinces, fall-applied N is often less effective than 
spring-applied N. The study was conducted to find reasons for inferiority of fall-applied 
N, and to determine the effect of various factors on the relative effectiveness of fall- 
versus spring-applied N and to investigate methods to improve the efficiency of fall- 
applied N. The poor performance of fall-applied urea was attributed to nitrification over 
the winter and subsequent denitrification in early spring after the snow melt. The loss of 
fall-applied N from mineral N pool was also caused by immobilization. The effectiveness 
of fall-applied N was improved by using ammonium-based fertilizers, delaying application 
in fall, and placing N fertilizer in widely-spaced bands and more so in nests or as large 
pellets. Inhibitors were also effective in increasing yield response of barley to fall-applied 
N, but may not be cost-effective. The relative efficiency of fall- versus spring-applied N 
was also increased with increasing N rate and soil test NO3-N level, fine texture, better 
drainage, drier soil conditions in fall and spring, and from Grey Luvisolic soil zone in 
northern to Brown soil zone in southern Alberta. 



RESUME 

En Alberta, tout comme dans les autres provinces des prairies, la fumure azotee appliquee 
en automne est souvent moins efficace que celle appliquee au printemps. Cette 6tude a ete 
entreprise pour en determiner les raisons et pour comparer l'effet de certains facteurs sur 
refficacite" de l'application de fumure azot6e automnale et printaniere et pour examiner des 
methodes qui pourraient ameliorer le rendement de la fumure azot6e automnale. La faible 
production associee a l'epandage d'uree automnale a €i€ attribute a une nitrification durant 
l'hiver suivie d'une denitrification apres la fonte des neiges. La perte de fumure azotee 
automnale du pool d'azote inorganique a aussi ete causee par immobilisation. On a 
ameliore l'application de fumure azotee automnale grace entre autres a l'utilisation de 
fertilisants a base d'ammonium, en retardant l'application plus tard a l'automne et en 
pla?ant un fertilisant a large granulomere, en bandes bien espacees. Des inhibiteurs ont 
accru le rendement de l'orge sur fumure azotee automnale meme s'ils peuvent s'averer non- 
rentables. On a 6galement ameliore refficacite relative de la fumure azotee automnale, en 
augmentant la teneur d'azote et d'azote nitrique du sol, avec une texture plus fine, un 
meilleur drainage, des conditions de sol plus sec a l'automne et au printemps et ce, de la 
zone des sols luvisoliques gris au nord de la province jusqu'a la zone des sols bruns au sud. 



INTRODUCTION 

In Alberta, and the other Prairie Provinces, nitrogen (N) fertilizers are often applied in 
fall rather than in spring for spring-sown crops. Fertilizing with N in the fall, rather than in the 
spring, has two main advantages - lower fertilizer prices and convenience. The main 
disadvantage is that yield increases from fall application can be considerably lower than those 
obtained from spring application (Table 1). The effectiveness of fall-applied N as compared to 
spring-applied N can be influenced by a number of factors. Management factors include: kind 
of N fertilizer, date of fall application, method of placement, use of nitrification inhibitors and 
slow-release N fertilizers, and straw handling. Other factors are: soil texture, drainage, fall soil 
moisture, soil-climatic zone, depth of placement and early growing season precipitation; rate of 
N, soil test nitrate-N level and yield response to applied N. This bulletin contains information 
for fertilizer dealers, agricultural extension personnel and farmers on the effect of these factors 
on the effectiveness of fall- versus spring-applied N. The information is based on field 
experiments, most of which were conducted in central and north-central Alberta. 

Table 1 Yield increase and N uptake of barley grain from fall and spring applications of urea 
incorporated into soil at 56 kg N/ha (average of 44 experiments) 



Time of N application Relative 

Measurement Fall Spring efficiency^ 

Increase in grain 970 1840 55 

yield (kg/ha) 

% recovery of 27 55 50 

applied N in grain 

^Relative efficiency was calculated as yield increase from fall-applied N, divided by yield increase from spring- 
applied N and multiplied by 100. 

REASONS FOR INFERIORITY OF FALL-APPLIED N 

Soil sampling of fall-fertilized plots from fall through winter has shown that fall 
incorporated urea slowly forms nitrate (nitrification) over the winter, even when soils are frozen 
(Table 2). Nitrate is subject to loss by denitrification (formation of nitrogen gases) when soil is 
wet and poorly aerated. In a number of experiments, early spring recovery of ^N-tagged 1 fall- 
applied N in soil was very low and the amount recovered was highly dependent on the kind of 
fertilizer applied (Table 3 and Fig. 1). Nitrogen loss was much greater from nitrate-based 
fertilizer than from ammonium-based fertilizer. Early spring N loss was primarily due to 



1 ^N is a heavy isotope of N that researchers use to track fertilizer N through the soil and plant. 
This provides an easy accounting of N applied. 



denitrification rather than leaching. Fall-applied N had not moved below the 60 cm depth 
(Table 3). Similar experiments with 15 N-tagged N indicate nitrate losses take place during 
episodes of mild weather in winter and during spring thaw whenever snow melts and the soil is 
wet. 

Table 2 Apparent nitrification of applied N during winter, after incorporation of urea at 56 kg 
N/ha on 6 October (average of 6 experiments) 



Fertilizer^ 
treatment 



% of applied urea N found as nitrate-N 



21 Oct. 



7 Dec. 



6 Mar. 



Urea - incorporated 


23 


Urea - banded 


8 


U+I - incorporated 


5 


U+I - banded 


1 



43 

19 

8 

2 



57 

25 

12 

5 



§ U+I refers to urea + inhibitor pelleted together in a ratio of 2:1, respectively. 



Table 3 The recovery of fall-applied 15 N-labelled fertilizers applied in October or December at 
1 12 kg N/ha from the soil N in the following May 







Percent recovery ( 


>f 15 N-labelled fall-applied 


N 


Soil 


Average 


of two experiments 


Average of three experiments 


depth 
(cm) 


KNO^ 

(incorp.)§ 


Urea 
(incorp.) 


(NH 4 ) 2 S0 4 
(banded) 


KNO^ 

(banded) 


(NH 4 ) 2 S0 4 
(banded) 


(NH 4 ) 2 S0 4 + 
thiourea (banded) 


0-15 


18 


46 


80 


15 


92 


97 


15-30 


23 


16 


3 


11 


2 


1 


30-60 


2 


1 





1 








60-90 




















90-120 
Total 




43 



63 




83 




27 



94 



98 



^Incorporated. 



lO 






100 
90 
80 
70 
60 
50 
40 



O 30 



20 - 



10 



II 



m 



ffl 



m 



Application Date: Q 8 ct £l^ Jun . 
Year. 
Source: 
Site: 



8 26 v i 
Oct. Oct .Mar. Jun. 

1982 I 1983 1982 I 1983 

Urea KN0 3 

Breton 



"] Losses by spring 

J Losses from spring until tall 

J S.E. for spring loss 

I S.E. for spring loss plus 
spring to fall loss 



in 



m 



a 



ffl 



m 



8 26 23 20 

Oct. Oct.iFeb May 

1982 I 1983 

Urea 



8 26 23 20 

Oct. Oct .Feb May 

1982 I 1983 

KNO3 



Innisfail 



Fig. 1. Loss of "N from soil at sowing and from soil and plants at harvest, with four dates of application for 
each fertilizer and site. 



FACTORS AFFECTING EFFICIENCY OF FALL- AND SPRING-APPLIED N 
Kind of N Fertilizer 



In a series of experiments, calcium nitrate and urea were incorporated into soil in the fall 
and average yields were lower with calcium nitrate than urea (Table 4). In four experiments 
comparing fall application of ammonium sulphate with urea, ammonium sulphate produced 
greater yields. In another four experiments, fall-applied ammonium nitrate yielded slightly less 
than fall-applied urea. These three sets of comparisons (Table 4) indicate that nitrate-based 
fertilizers are often inferior to ammonium-based fertilizers when applied in the fall. 



Table 4 Yield increase and N uptake of barley grain with fall and spring incorporation 
applications of N fertilizers at 56 kg N/ha in field experiments 







Increase in 


% recovery 


Relative 


Relative 






grain yield 


of applied N 


efficiency 


efficiency (N 


No. of tests 


Treatment^ 


(kg/ha) 


in grain 


(Yield)t 


recovery)t 


21 


CN-fall 


802 


21 


48 


41 




Urea-fall 


940 


26 


56 


51 




Urea-spring 


1683 


51 






4 


AS-fall 


1435 


37 


61 


54 




Urea-fall 


1130 


31 


48 


45 




Urea-spring 


2335 


69 






4 


AN-fall 


750 


24 


58 


59 




Urea-fall 


848 


27 


66 


66 




Urea-spring 


1285 


41 







§CN, AS and AN refer to calcium nitrate, ammonium sulphate and ammonium nitrate, respectively. 
^Relative efficiency was calculated as yield increase (or N recovery) from fall-applied N, divided by yield 
increase (or N recovery) from spring-applied N and multiplied by 100. 



Date of Fall Application 



Nitrification rates in soil are positively correlated to soil temperature. As a result, 
conversion of added ammonium to nitrate should be greater with early fall when soils are warm 
than with late fall application when soils are cool. Soil temperature steadily decreases from mid- 
September to early November when the soil begins to freeze (Figure 2). One would thus expect 
more over-winter loss of fall-applied N and subsequently lower N uptake and yield of the crop, 
with the application of ammonium fertilizers in early as compared to late fall. To investigate 
this scenario, 15 experiments were conducted in which urea was broadcast and incorporated at 2 
or 3 dates in the fall. The recovery of mineral N (ammonium plus nitrate) in the spring was 
greater when applications were made in late fall as compared to early fall (Figure 3). The % 
recovery of fall-applied N as soil mineral N found in spring increased from 31% with urea added 
on 20 September to 73% with urea applied on 31 October (based on the linear regression). 

Fall incorporated urea produced less barley yield relative to urea applied in the spring 
(Figure 4). Delaying application in the fall markedly improved yield response. Yield increase 
from fall-applied N as a % of yield increase from spring-applied N rose from 23% for urea 



o 

o 

CD 
Z3 
03 

a5 

Q. 

E 

(D 



O 
CO 



16 
14 

12 
10 
8 
6 
4 
2 
0- 
-2 
-4 
12 
10 
8 
6 
4 
2 

-2 




110 



Lacombe 




Ellerslie 



J. 



Sept. 15 Sept. 30 Oct. 15 
Date 



Oct. 30 Nov. 14 



100 



Q. 
V) 



o 

CO 

c 



CL 

Cl 

< 



o 

CD 

> 

o 
o 

CD 
0C 



90 



80 



70 



60 



Co* relator cocfltctenl (') : M" 
Y = »0t •* to?* 

WhC'e X - Nwmbet O* OJ-yi •"— '--(- IS 



S 50 



40 



30 



20 



10 




15 30 45 60 

Sept. IS Sept 30 Oct. 1S Oct 30 Nov. 14 

Date of Fall Application 



Fig. 2 Mean daily soil temperature in the morning (6 or 8 h) and the Fig. 3 Effect of date of N application in fall on the recovery of 

afternoon (17 or 18 h) at 5 cm depth at meteorological stations applied N as mineral N in soil in spring from urea at N rates of 

in Ellerslie (northcentral Alberta) and Lacombe (central 50 or 56 kg/ha. 
Alberta), averaged from 1975 to 1984 



100 



z 90 
■D 

a 80 

ci 

< 



c 



CL 



70 



60 



50 



40 



<D 
</) 
CO 



O 

£ SOF- 



TS 
oj 
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<D 

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20 



J2 10 



Correlation coeHicieni (r)=068" 

¥ = UB < 1 09K 
Where X - Nunttef o) day* aiw* Sccn IS 
Y = RHaii<>« y«*d «nc«ease ot 
Fan* vfw Sprtng-appfccd N 









Sept. 15 



15 
Sept 30 



30 
Oct 15 



45 
Oct. 30 



60 

Nov 14 



TO 

a. 

Q. 

< 

1 

c 

Q. 



CO 



TO 

3 



0) 

TO 
O 

tr 



IUU 




Correlation coetlicienl <r)=066" 








90 






X = 


17« « 1BSX 










Where 


x = 


Number o* dan atler Sept IS 














Y = 


Relative % N wee— y of 
Fan- wertui Sprtng-apphed N 




• 
• 


• 


80 










• 




• 


70 








• 


> 

• 




• 


60 








• 
*• 

• / 




• 
• 


• 


50 








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m/ «i 














•/ 
















• / 








40 






• 


• / 

/ * 
/ * 






# 


30 




• 












20 


- 




• 


• 

• 

• • 








10 

n 




1 




• 

1 1 






1 



Date of Fall Application 



15 30 45 60 

Sept. 15 Sept 30 Oct 15 Oct 30 Nov. 14 

Date of Fall Application 



Fig. 4 Effect of dale of N application in fall on relative yield increase Fig. 5 Effect of date of N application in fall on N uptake in barley 
of barley grain from fall- versus spring-applied urea at N rates grain from fall-applied urea relative to spring-applied urea at 

of 50 or 56 kg/ha. N rates of 50 or 56 kg/ha. 



Table 5 The recovery of applied N as ammonium-N and mineral N in soil (0-90 cm) in May, 
yield increase and N uptake of barley grain with the application of urea and U+I§ (2:1) in 
October at 56 kg N/ha (average of 10 field experiments) 







N applied 


in fall 




N applied 
Urea- 


in spring 




Urea- 


Urea- 


U+I- 


U+I- 


Urea- 


Parameter 


Incorp.t 


Banded 


Incorp.t 


Banded 


Incorp.t 


Banded 


% recovery in soil as 


8 


15 


30 


46 






ammonium-N 














% recovery in soil as 
mineral N 


62 


68 


75 


85 






Increase in grain yield 
(kg/ha) 


1070 


1250 


1440 


1740 


2000 


2090 


% recovery of applied N 


31 


37 


44 


57 


63 


67 


in grain 















»U+I (2:1) refers to urea + inhibitor pelleted together in a ratio of 2:1, respectively. Thiorea is a nitrification 

inhibitor. 

t Incorporated. 



Table 6 Grain yield increase and % recovery of applied N in grain and in soil in spring from 
urea solution and aqua NH3 with and without inhibitors banded in fall and spring (average of 6 
experiments for aqua NH3 and 10 experiments for solution urea) 







Yield 
increase 
(kg/ha) 




% recovery of applied Is 


f 


Fertilizer 


In grain 


In soil (0-30 


cm) 


treatment^ 


Ammonium-N 


Mineral N 


Aqua NH r fall 




763 


26 


1 


49 


Aqua NH3 + Inhibitors ■ 


■fall 


1144 


41 


18 


69 


Aqua NH^-spring 




1557 


55 






Urea-fall 




972 


29 


4 


44 


Urea + Inhibitors - fall 




1358 


40 


34 


73 


Urea-spring 




1853 


61 







^Inhibitors used were ATC, N-Serve 24E, CS2, (NH 4 ) 2 CS3, K 2 CS 3 and thiourea applied at 2, 4, 10, 20, 24 and 
45 kg/ha, respectively. 



applied on 20 September to 69% for urea applied on 31 October. The values of N uptake by 
barley showed similar pattern to yield increase values (Figure 5). The N uptake was greater 
with late fall compared to early fall application. 

The efficiency of fall incorporated urea as compared to spring incorporated urea varied 
greatly from experiment to experiment. This is not unexpected as the experiments were 
conducted on a variety of soils over a number of years. Nevertheless, early fall application for 
barley was inefficient while application in late fall at times achieved efficiencies close to spring 
application (Figures 4 and 5). Keep in mind, however, that these experiments used incorporated 
urea. Banding which tends to increase the efficiency of fall application, may be less sensitive to 
application date. 

Inhibitors and Slow Release N Fertilizers 

Ammonium can neither easily leach from soil nor is it subject to denitrification in soil. 
Nitrate can be lost through both mechanisms. Inhibitors, which suppress the formation of nitrate 
from ammonium-based fertilizers, should reduce over-winter loss of fall-applied N and increase 
crop yield. A number of inhibitors (thiourea, ATC, N-Serve 24E, CS2, (NH 4 ) 2 CS3 and K2CS3) 
were tested with urea or aqueous NH 3 . These inhibitors were all effective in suppressing 
nitrification of fall-applied N (Tables 2, 5 and 6) and in reducing over-winter N losses, 
especially when the N fertilizer plus inhibitor were placed in bands (Tables 5 and 6). In most 
cases, these reduced losses translated into substantial increases in barley yield (Tables 5 and 6). 
However, placing fertilizer in concentrated bands or nests was equal or better than the inhibitors 
(see section on Methods of N Placement). 

This research tested only one slow-release N fertilizer, sulphur-coated urea (SCU). 
Sulphur-coated urea was not effective in improving the effectiveness of fall-applied N and it 
gave poor barley yields when applied in the spring. The explanation was that N release from 
SCU was too slow to meet the crop needs. 

Methods of N Placement 

Nitrification inhibitors were effective in improving barley yield response to fall-applied 
N. However, they may not be convenient to apply with N fertilizers or cost-effective. In 
addition, many of the inhibitors were found to slow the release of mineral N from native soil N. 
Therefore, field experiments were conducted to find if the effectiveness of fall-applied urea 
could be improved by concentrating the fertilizer through placement in bands, and in nests or as 
large pellets. 

Yield and recovery of applied N in barley grain were considerably lower with fall 
application than spring application in four experiments comparing broadcast, incorporated and 
banded (22.5 cm spacing) applications (Table 7). Overall, broadcast application was least 
effective and band placement was most effective. Nevertheless, yields with fall banding were 
still inferior to those with spring banding. 

Experiments were conducted with further concentration of urea or aqua NH3 by placing 
in widely-spaced bands (45 cm spacing) or in nests or as large pellets. The nest method of 
application was performed by placing a number of commercial fertilizer granules at a point 



Table 7 Yield increase and % recovery of applied N in barley grain with fall and spring 
applications of urea at 56 kg N/ha following different methods of placement (average of 4 
experiments) 



Fall-applied N Spring-applied N 

Parameter Broadcast^ Incorp.t Banded* Broadcast Incorp.t Banded 



Increase in grain 
yield (kg/ha) 

% recovery of 
applied N in grain 



543 848 1018 998 1285 1425 

18 27 33 31 41 46 



§ Surface broadcast. 

t Incorporation. 

tBands were 22.5 cm apart. 



below the soil surface. For the large pellet method, urea pellets ranged from 1- to 3-g weights. 
Single pellets were placed below the surface on a fixed grid. Grid spacings increased with pellet 
size in order to give the same N rate in all treatments. The main purpose of bands, nests or 
pellets is to keep the fall-applied N in ammonium form by reducing the contact area between 
fertilizer and soil. 

Almost all of the fall-applied incorporated urea granules nitrified by May (Table 8). The 
recovery of applied N as NH 4 -N increased markedly when the fertilizer was banded or nested. 
The recovery of applied N in mineral N was also much greater with banding and even greater 
with nesting than mixing, indicating that over-winter N losses were reduced substantially when 
urea was placed in bands or nests. Yield and recovery of applied N in grain was also improved 
(Table 8). The barley yields with nests of urea were very close to those obtained with spring- 
applied N. The results were similar with aqua NH3 placed in bands or nests. In a few 
experiments, nitrification inhibitors were used with nest placement, but there was no further 
improvement in crop yield from the use of inhibitors. 

When straw is returned to the field, it tends to temporarily immobilize N and can affect 
the amount of fertilizer N available for the next crop. Two field experiments investigated 
whether or not the effect of straw can be minimized by placing N fertilizer in bands or in nests 
or as large pellets. For fall-applied N, placing urea in nests improved barley yields and N use 
efficiency in both straw-off and straw-on treatments, though yields were slightly lower when 
straw was retained than when it was removed (Table 9). With spring-applied N, the yield 
difference between straw-off and straw-on plots was 625 kg/ha for the incorporation application 
and only 190 kg/ha when the fertilizer was banded at sowing. Apparently, less of the applied N 
will be immobilized in the soil organic matter as shown by the ^N experiments (Table 10). 
This leaves more fertilizer N for crop uptake. 



Table 8 Effect of method of placement on yield increase and % recovery of applied N in grain 
and in soil in May from urea applied at 50 or 56 kg N/ha in the fall and in the spring (average of 
20 experiments) 





Yield 
increase 
(kg/ha) 




% recovery of applied N 


Fertilizer 


In grain 


In soil 


(0- 


60 cm) 


treatment^ 


NH 4 -N 




Mineral N 


Urea incorp.t-fall 


839 


23 


4 




42 


Urea banded-fall 


1238(950) 


36(26)$ 


20(16) 




66(52) 


Urea nested-fall 


1509(1535) 


46(45) 


50(36) 




77(84) 


Urea incorp.t-spring 


1644(1763) 


51(54) 









§Bands were 45 cm apart. In 7 experiments urea nested was 2-g, or 2.5-g pellets. 

t Incorporation. 

tin brackets are the results with aqua NH3 in four experiments. 



These experiments indicate that banding and nest placement or large urea granules are 
good alternative to chemical nitrification inhibitors for conserving fall-applied N both from 
economical and environmental point of view. Use of concentrated placement in bands or nests 
allows effecient production, reduces the potential of environmental impact from nitrate leaching 
and denitrification and incurs no added chemical expenses. 

Six field experiments were conducted to answer the question of whether or not large urea 
pellets are as effective as commercial urea when applied in spring. Urea placed in nests or as 
large pellets (2-g or larger) at sowing was much less effective in increasing barley yield than 
commercial urea incorporated into the soil just prior to sowing or side banded at sowing 
(average yield increase was 853 kg/ha for large urea pellets and 1517 kg/ha for commercial 
urea). In one experiment, yield response to applied N decreased from 1240 kg/ha with 1-g 
pellets to 490 kg/ha with 3-g pellets. The main reason for this poor performance of large pellets 
applied in spring was the slow diffusion of N from the pellet to the plant roots and essentially the 
fertilizer N in pellets becomes isolated from many of the growing plants for a period of time in 
the early peak growing season. 

In the Prairie Provinces, denitrification of spring-applied N fertilizers (as opposed to fall- 
applied N) is not a serious problem in most years. Thus spring-applied nest or large pellets are 
of no particular advantage. Any risk of N loss from spring-applied N can be easily overcome by 
banding and does not need the use of large pellets. 



Table 9 Influence of disposal of straw of the previous crop and method of N placement on grain 
yield of barley and N use efficiency with fall and spring application of urea at 50 kg N/ha 
(average of 2 experiments) 





Grain yield (kg/ha) 
Straw-Off Straw-On 


N use efficiency 

(kg grain/kg N) 

Straw-Off Straw-On 


% 
of 


recovery 
applied N 


Fertilizer treatment^ 


Straw-Off Straw-On 


Control 


2065 


1665 










Urea incorp.t-fall 


2815 


2740 


15.0 


21.5 


35 


30 


Urea banded-fall 


3210 


2815 


22.9 


23.0 


40 


32 


Urea pellets-fall 


3300 


3105 


24.7 


28.8 


43 


54 


Urea incorp.t-spring 


3435 


2810 


27.4 


22.9 


49 


42 


Urea-banded-spring 


3460 


3270 


27.9 


32.1 


54 


53 



§Fall bands were 45 cm apart. Pellets contained 2-g of urea. In spring urea was banded 4 cm beside and below 

the seed row. 

'Incorporation. 



Table 10 Influence of method of placement and straw addition on the recovery of 15 N-labelled 
urea applied at 50 kg N/ha at sowing, in barley plants and soil at harvest 





Method of 
placement 






% recovery 


of applied N 






In 


plants 




In soil 




Location 


Without 
straw 




With 
straw 


Without 
straw 


With 
straw 


Rimbey 
Ellerslie 


Incorp.§ 
Banded 

Nested 

Incorp.§ 
Banded 

Nested 


60.1 
73.9 
76.0 

11.8 
27.1 
50.8 




51.7 
71.0 
77.8 

13.8 
27.6 
46.6 


29.9 
18.8 
15.8 

36.4 
22.0 
22.0 


36.9 

21.2 
20.7 

48.9 
26.9 
26.9 


^Incorporation. 















10 



Depth of Placement of Spring-Applied N 

The availability of fertilizer N to the crop can be affected by its position in relation to 
plant roots. Under dryland conditions the upper most layer of soil generally dries out early in 
the cropping season. Roots near the surface become inactive and do not take up nutrients. As a 
result, fertilizer is "stranded" in this dry surface layer (J.T. Harapiak-Personal Communication). 
Furthermore, N fertilizer, especially urea, at or near the surface is vulnerable to loss through 
ammonia volatilization. This can limit crop response to the applied N. Field experiments were 
conducted to study the effects depth of N fertilizer placement on crop growth (Table 11). In 
four experiments (No. 18-21), the yield benefit of urea incorporated to a depth of 10-12 cm over 
surface-applied urea amounted to 290 kg/ha, while the advantage of banding over surface- 
applied urea was 430 kg/ha. 

In another experiment (No. 8), grain yield was much higher for deeper incorporation and 
for deeper banding as compared to shallow incorporation or banding. In this experiment, depth 
of shallow incorporation or shallow banding was not more than 4 cm and surface soil was very 
dry during the early part of the growing season. In the shallow incorporation treatment, it is 
likely that the fertilizer N was "stranded" near the surface and was not available to plants early in 
the growing season. In the other experiments under more favourable moisture conditions, there 
were little or no differences in yield between shallow and deep placements. 

These results indicate that the response to applied N can be modified by the depth at 
which the fertilizer is applied. The advantage of deep placements over shallow placement 
appears to be offset if rainfall occurs soon after fertilizer application. The advantage is likely to 
be greater during relatively dry years when the fertilizer is "stranded" during the key early 
growth stages. This lower yield with shallow spring-applied N can mask the relative difference 
between fall- and spring-applied N. 

Rate of N, Soil Test NO3-N Level and Yield Response 

In general, the yield response to each additional increment of applied N normally 
decreases with increasing rate of N. Therefore, one would expect smaller relative yield 
difference between fall- versus spring-applied N (relatively) when the rate of fertilizer is high. 
Eight field experiments were conducted to determine the effect of rate of urea N on the relative 
efficiency of fall- versus spring-applied N (Table 12). The differences between fall- and spring- 
applied N for N use efficiency and % N recovery of applied N decreased, as N rate increased. 
The relative efficiency of fall- versus spring-applied urea increased from 47 to 73% when the N 
rate was increased from 25 to 100 kg N/ha. This does not imply that high N rates reduce over- 
winter loss, but instead they mask the differences between fall and spring-applied N. The use of 
extra N fertilizer to compensate for the over-winter N loss is neither an economical nor an 
environmentally sound practice. Other techniques such as banding or nesting or large pellets 
should be used to improve the effectiveness of fall-applied N. 



11 



Table 1 1 Effect of depth of placement of urea, on grain yield of barley, applied at time of 
sowing in 33 field experiments in central and north-central Alberta 





Control 

Shallow- 

tilled§ 


Control 
Deep- 
tilled§ 




Yield of barley 


grain (kg/ha) 




Experiment 
number 


Urea 
Shallow- 
tilled 
Shallow- 
incorporated 


Urea 
Deep-tilled 

Deep- 
incorporated 


Urea 
Shallow- 
tilled 
Shallow- 
banded 


Urea 

Deep-tilled 

Deep-banded 


1-4 


2020 


2860 


3880 


3890 






5-7 


1960 


1980 


2930 


2880 


3160 


3180 


8 


mot 


2100 


1790t 


3090 


2460 


3390 


9-17 




1520 




3750 


3830 




18-21 




1100 


2090* 


2380 


2520 




22-33 


1900 




2740 




2770 





§Shallow-tilled (5 to 7 cm depth) and Deep-tilled (10 to 12 cm depth). 

^The plots were tilled to a depth of less than 4 cm. 

+Urea was broadcast and not incorporated into soil in these experiments. 



Yield response to fertilizer N also decreases with increasing levels of plant-available N in 
soil. In our work in central Alberta, there was little response to fall- or spring-applied N on soils 
with large amounts of NO3-N as compared to soils with low levels of NO3-N (data not shown). 

Texture, Drainage and Fall Soil Moisture 

To determine the effect of soil conditions on the relative efficiency of fall- versus spring- 
applied urea, field sites were separated by texture, drainage and wetness of soil in the fall (Table 
13). The sites with imperfect drainage, soil moisture above field capacity in fall and coarse to 
medium texture tended to show lower relative efficiency of N use than the sites with good to 
moderate drainage, soil moisture below field capacity in fall and fine to very fine texture. 

Soil-Climatic Zone 

Laboratory incubation studies showed that soils in all agro-climatic zones in Alberta have 
similar potentials for NO3-N loss under anaerobic conditions (Table 14), but the actual loss from 
fall-applied N in the field depends on soil-climatic conditions. The Brown and Dark Brown soil 
zones are relatively dry and soils seldom become water saturated during the spring thaw. While 



12 



Table 12 Effect of N rate on N use efficiency, % recovery of applied N in grain and relative 
efficiency of fall- versus spring-applied urea (average of 8 experiments) 



Rate of N 
(kg N/ha) 


Time of 
application 


N use 

efficiency 

(kg of grain 

/kg of N) 


% recovery 
of applied 
N in grain 


Relative 

efficiency 

(yield)§ 


Relative 

efficiency 

(N recovery)^ 


25 


Fall 


15.7 


20.0 


47 


42 




Spring 


34.1 


48.9 






50 


Fall 


16.6 


25.8 


59 


60 




Spring 


28.9 


43.7 






100 


Fall 


15.8 


27.1 


73 


69 




Spring 


20.0 


34.9 







^Relative efficiency was calculated as yield increase (or N recovery) from fall-applied N, divided by yield 
increase (or N recovery) from spring-applied N and multiplied by 100. 

Black and Gray Luvisolic zones are relatively moist and soils are usually water saturated for 
several days after the snow thaw. Field experiments using 15 N-labelled KNO3 were carried out 
from Beaverlodge in northern Alberta to Lefhbridge in southern Alberta to determine the over- 
winter loss of winter-applied N in various soil zones of Alberta (Table 14). The over-winter loss 
of applied N was much greater in the central and northern portions than in the southern portions 
of Alberta. However, these experiments were conducted only one year and the values given in 
Table 14 would differ in other years depending on localized climatic conditions. 

The results of 99 field experiments were summarized to compare the yield response of 
barley or wheat to fall- versus spring-applied urea incorporated into soil in different soil zones in 
Alberta (Table 15). The relative efficiency of fall-versus spring-applied N was lower in the 
Gray Luvisol and Black soil zones as compared to Dark Brown and Brown soils zones. 

CONCLUSIONS 

Fall-applied N was inferior to spring-applied N because of substantial over-winter 
nitrification and subsequent N loss in early spring through denitrification. Over-winter N loss 
was greater from nitrate than from ammonium, and ammonium-based fertilizers were more 
effective than nitrate-based fertilizers in increasing yield of barley. 

The effectiveness of fall-applied N was greatly improved by placing urea in widely- 
spaced bands and more so by placement in nests or as large pellets. This increased effectiveness 



13 



Table 13 Effect of factors on the yield increase and N recovery of fall versus spring applications 
of urea at 56 kg N/ha in 44 field experiments 







Relative 


Relative efficiency 


Factors 


No. of expts. 


efficiency (Yield)§ 


(N 


recovery)^ 


Texture 










Coarse to medium 


26 


51 




46 


Fine to very fine 


18 


61 




56 


Drainage 










Well to mod. well 


32 


57 




51 


Imperfect 


12 


47 




44 


Fall moisture 










<75%ofFCt 


12 


62 




55 


75 to 100% FC 


20 


56 




52 


>FC 


12 


46 




42 



^Relative efficiency was calculated as yield increase (or N recovery) from fall-applied N, divided by yield 
increase (or N recovery) from spring-applied N and multipled by 100. 
^FC (field capacity) refers to moisture content in soil at 33 kPa. 



Table 14. Denitrification potential and actual over-winter N loss from winter-applied 15 N- 
labelled KNO3 in soils from northern to southern Alberta 







Denitrification 










potential 


% of winter-applied 


Location 


Area of Alberta 


(mg N/kg soil/day) 


Nlost 


over the winter 


Beaverlodge 


Northern 


19 




93 


Ellerslie 


North-central 


20 




79 


Rim bey 


Central 


23 




74 


Calgary 


South-central 


21 




30 


Granum -Vauxhall 


Southern 


22 




18 



14 



Table 15 The relative efficiency of fall- versus spring-incorporated§ N in various soil zones t 



Soil zone 


No. 


of sites 


Relative 

efficiency 

(Yield)* 


No. 


of sites 


Relative 
efficiency 

(N recovery)! 


Luvisolic 




17 


63 




16 


63 


Black 




54 


73 




48 


66 


Dark Brown 




15 


86 




11 


80 


Brown 




13 


97 




13 


89 



§The N fertilizer was incorporated to a depth of 5 to 7 cm in most of the experiments in the Brown and Dark 

Brown soil zones and about one-third of the experiments in the Luvisolic and Black soil zones, and to a depth of 

10 cm in other experiments, 
t Relative efficiency was calculated as yield increase (or N recovery) from fall-applied N, divided by yield 

increase (or N uptake) from spring-applied N and multiplied by 100. 
^Source - Bole et al. 1984. Regional and environmental influence on N use efficiency. Pages 1-29 in Proc. 

Alberta Soil Science Workshop, 21-22 Feb. 1984, Edmonton, Alberta. 



was due to slower nitrification and possibly reduced immobilization of applied N by banding or 
nesting as compared to incorporation. Surface-broadcasting was least effective. Delaying urea 
application in fall until close to freeze-up also improved the efficiency of fall-applied N. Spring 
application of urea in nests or as large pellets reduced yield response because the fertilizer 
becomes spatially unavailable to plants for a period of time in early peak growing season. 

Inhibitors were effective in slowing nitrification, reducing over- winter N loss and 
improving yield response of barley to fall-applied N. However, inhibitors may be inconvenient 
to apply and may not be cost-effective. Sulphur-coated urea (a slow-release fertilizer) was not 
effective in improving the efficiency of fall- or spring-applied N. 

The relative efficiency of fall- versus spring-applied N increased with increasing N rate, 
increasing soil test NO3-N level, finer texture, better drainage, and drier soil conditions in fall 
and early spring. Over-winter N loss was greatest in the Gray Luvisolic soil zone and least in 
the Brown soil zone. 

RECOMMENDATIONS 

1. Use ammonium-based N fertilizers for fall application. 

2. Apply N fertilizer in widely-spaced bands below the soil surface or use any other 
fertilizer application technique which reduces soil-fertilizer contact. 

3. Delay fall application to as close to freeze-up as possible. 



15 



4. For maximum benefit from spring-applied N, incorporate N fertilizer to a depth of 10-12 

cm or band below seeding depth. 

REFERENCES 

Bole, J.B.; Harapiak, J.T.; Malhi, S.S.; Penney, D.C. 1984. Regional and environmental 
influence on nitrogen use efficiency. In Proceedings of Alberta Soil Science Workshop, 
pp. 1-18. 

Heaney, D.G.; Blades, A.T.; Malhi, S.S.; Nyborg, M. 1984. Over-winter mineralization, 
immobilization and denitrification of mineral nitrogen. In Proceedings of Alberta Soil 
Science Workshop, pp. 46-59. 

Heaney, D.J.; Nyborg, M.; Solberg, E.D.; Malhi, S.S.; Ashworth, J. 1992. Overwinter nitrate 
loss and denitrification potential of cultivated soils in Alberta. Soil Biol. Biochem. 24: 

877-884. 

Malhi, S.S.; McGill, W.B. 1982. Effect of temperature, moisture, and substrate concentration on 
the rate of nitrification. Soil Biol. Biochem. 14:393-399. 

Malhi, S.S.; Nyborg, M. 1979. Nitrate formation during winter from fall-applied urea. Soil 
Biol. Biochem. 11:439-441. 

Malhi, S.S.; Nyborg, M. 1982. An evaluation of carbon disulphide as a sulphur fertilizer and as 
a nitrification inhibitor. Plant and Soil 65:203-218. 

Malhi, S.S.; Nyborg, M. 1983. Field study of the fate of fall-applied 15 N in three Alberta soils. 
Agron. J. 75:71-74. 

Malhi, S.S.; Nyborg, M. 1983. Release of mineral N from soils: Influence of inhibitors of 
nitrification. Soil Biol. Biochem. 15:581-585. 

Malhi, S.S.; Nyborg, M. 1984. Inhibiting nitrification and increasing yield of barley by band 
placement of thiourea with fall-applied urea. Plant and Soil 77: 193-206. 

Malhi, S.S.; Nyborg, M. 1984. Methods of placement for increasing the efficiency of N 
fertilizers applied in the fall. Agron. J. 77:27-32. 

Malhi, S.S.; Nyborg, M. 1986. Increase in mineral N in soils during winter and loss of mineral 
N during early spring in north-central Alberta. Can. J. Soil Sci. 66:397-409. 

Malhi, S.S.; Nyborg, M. 1988. Effect of ATC, N-Serve 24E and thiourea nitrification inhibitors 
on yield and N uptake of barley fertilized with fall-applied N. Plant Soil 105:223-229. 



16 



Malhi, S.S.; Nyborg, M. 1988. Control of nitrification of fertilizer nitrogen: Effect of inhibitors, 
banding and nesting. Plant Soil 107:245-250. 

Malhi, S.S.; Nyborg, M. 1990. Efficiency of fall-applied urea for barley: Influence of date of 
application. Fert. Res. 22:141-145. 

Malhi, S.S.: Nyborg, M. 1991. Recovery of 15 N-labelled urea: Influence of zero tillage, and 
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Malhi, S.S.; McGill, W.B.; Nyborg, M. 1990. Nitrate losses in soils: Effect of temperature, 
moisture and substrate concentration. Soil Biol. Biochem. 22:733-737. 

Malhi, S.S.; Nyborg, M. 1992. Fall- versus spring-applied urea: Influence of N rate. Commun. 
Soil Sci. Plant Anal. 23: 301-312. 

Malhi, S.S.; Nyborg, M.; Solberg, E.D. 1989. Recovery of 15 N-labelled urea as influenced by 
straw addition and method of placement. Can. J. Soil Sci. 69:543-550. 

Monreal, C. 1981. Nest placement of nitrogen fertilizers. M.Sc. Thesis. University of Alberta, 
Edmonton, Canada. 

Nuttal, W.S.; Dawley, W.K.; Malhi, S.S.; Bowren, K.E. 1989. The effect of spring and fall 
application of N on yield and quality of barley (Hordeum vulgar e L.) and rapeseed 
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Nyborg, M.; Malhi, S.S. 1979. Increasing the efficiency of fall-applied urea fertilizer by placing 
in big pellets or in nests. Plant and Soil 52:461-465. 

Nyborg, M.; Malhi, S.S. 1986. Comparison of fall and spring application of nitrogen fertilizers 
in northern and central Alberta. Can. J. Soil Sci. 66:225-236. 

Nyborg, M.; Malhi, S.S.; Solberg, E.D. 1990. Effect of date of application on the fate of 15 N- 
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Nyborg, M.; Malhi S.S. 1992. Effectiveness of fall-versus spring-applied urea on barley: Pellet 
size and depth of placement. Fert. Res. 31: 235-239. 



17 




3 ^073 000^S33T